The purpose of this research is to evaluate the impact of emergency and post-disaster mental health services for New York City (NYC) residents following the World Trade Center disaster (WTCD). Although little data yet exist on the full impact of the WTCD on NYC residents, anecdotal reports suggest that many residents have been suffering from anxiety, depression, irritability, and other psychological disturbances. Adding to the anxiety and uncertainty in the NYC is the economic uncertainty created by this disaster and the ongoing threat of future terrorism. Recent reports suggest that the availability of mental health services following this disaster has been extensive. We anticipate that the proposed study can evaluate the effectiveness of both emergency and post-disaster mental health services for NYC residents and help guide future health care planning. To achieve this, we propose a longitudinal cohort study of 2,500 NYC residents. This study is needed to address issues related to treatment effectiveness, access to care, and the quality of mental health care for stress-related disorders following the WTCD. Study participants would include adults (18 years and over) in NYC randomly selected by a telephone survey and would involve 1,250 adults who received mental health treatment following the WTCD (the treatment cohort) and 1,250 adults who did not receive this treatment (the non-treatment cohort). For this study, we would conduct a baseline survey one-year after the WTCD and a follow-up survey one-year after the baseline (24 months post-disaster). The enormous scope of this disaster, together with the treatment response of emergency service agencies, mental health organizations, and health care providers in NYC, provide a unique opportunity to evaluate mental health interventions among a diverse urban population. Valid and reliable data related to effectiveness, access, and the quality of mental health services for traumatic stress disorders are extremely important. Under a separate grant application, we have submitted a proposal to conduct a community mental health study. This current proposal represents a non-overlapping grant with a different methodology; it focuses on treatment outcomes rather than on community epidemiology, which was the focus of our previous application. In this current study, we plan to use advanced psychometric assessments and established health services survey methods, concurrent with established multivariate modeling, to evaluate the impact of specific mental health interventions on a broad spectrum of psychological and social outcomes.